One of the more interesting recent questions in behavioral biology concerns the probable function of dialects in birds. It has been proposed that dialects have arisen as adaptive modifications in response to ecological pressures and that this has produced a tendency toward positive assortative mating. We have studied the reproductive success, dispersal patterns, and response to song playback of the sedentary Nuttal subspecies of the White-crowned Sparrow (Zonotrichia leucophrys). These data seem to be more compatible with some type of social adaptation model such as that proposed by Payne than with the expectations of the assortative mating hypothesis. In addition, we have determined the song types of a few mated pairs and find no evidence for positive mating. This research program will continue our studies of dispersal and reproductive success. We will continue the playback studies to resolve some of the ambiguities in the present data and will inject some additional females with testosterone to determine the song types of additional pairs. These converging lines of evidence will then be brought to bear on the alternative theories that have been proposed to account for dialects in avian species.